This invention is concerned with a system by which a tubing string is suspendable within a wellhead and is particularly concerned with an improved installable load shoulder by which a tubing hanger is supported in a wellhead. "Tubing" or "tubing string" as used herein is inclusive of any tubular product used in drilling and completing oil or gas wells and is particularly inclusive of casing. A feature of this invention is an improved installable load shoulder that may be removably positioned in a wellhead to support a tubing hanger and which can be thereafter removed.
When a borehole in the earth is completed it is customary to attach to the upper end of the well structure a wellhead which provides the superstructure for supporting smaller diameter tubular strings. As an example, a common expedient is to suspend within a casing string a tubing string that is supported by a wellhead. For this purpose it is traditional to employ a tubing hanger that is secured to a length of tubing and accordingly means must be provided to support the tubing hanger to or within the wellhead.
A common procedure is to provide in the wellhead an internally extending circumferential ledge upon which a tubing hanger can rest. A problem with this arrangement is that the provision of an internally extending ledge within the interior of a wellhead reduces the internal diameter of the wellhead and thereby limits the diameter of drill bits or other tools or implements that may thereafter be inserted through the wellhead. This invention provides a means of supporting a tubing hanger within a wellhead in a manner such that the normal internal diameter of the wellhead is not reduced, that is, where the wellhead has a full internal diameter open while nevertheless providing means for supporting a tubing hanger. For background information regarding wellhead assemblies, and apparatus for suspending tubing within a wellhead, reference may be had to the following previously issued United States patents:
______________________________________ U.S. PAT. NO. INVENTOR TITLE ______________________________________ 3,341,227 Pierce Jr. Casing Hanger 3,893,717 Nelson Well Casing Hanger Assembly 3,918,747 Putch Well Suspension System 4,167,970 Cowan Hanger Apparatus For Suspending Pipes 4,515,400 Milberger et al Mudline Casing Hanger Assembly 4,751,968 Ames et al Wellhead Stabilizing Member With Deflecting Ribs 4,770,249 Courtney Method and Apparatus For Reduction of Well Assembly Time 4,903,992 Jennings et al Locking Ring For Oil Well Tool 5,060,985 Seaton Location of Tubular Members 5,209,521 Osborne Expanding Load Shoulder 5,259,459 Valka Subsea Wellhead Tieback Connector 5,327,965 Stephen et al Wellhead Completion System ______________________________________